Incorporated Sorghum Residues Reduce Emergence and Seedling Growth of Some Crops

Handsen Tibugari,Stanford Mabasa,Cornelius Chiduza,Arnold Bray Mashingaidze

doi:10.7764/ijanr.v48i2.2298

Abstract

Allelochemicals from sorghum [Sorghum bicolor (L.) Moench] residues may inhibit the emergence and growth of other crops. We examined the effects of residues from two sorghum landraces, IS9456, a high sorgoleone producer, and IS22320, a zero sorgoleone producer. Residues were applied at 7.2 g, 14.4 g and 21.6 g kg-1 of soil. Emergence and the growth of maize (Zea mays L.), wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] were tested in three glasshouse pot experiments at the University of Zimbabwe in 2017. The 2×3 factorial experiments were laid as a randomized complete block design with six replications. Residues from IS22320 significantly (P<0.05) reduced the emergence of maize by 22.2% compared to residues from IS9456. Sorghum variety as a source of residue did not significantly (P>0.05) reduce the emergence, height, chlorophyll content or dry weight of soybean. Increasing the residue rate significantly (P<0.05) reduced the percent emergence, height, chlorophyll content and dry weight of soybean. There was a significant sorghum variety × residue application rate interaction on the percent emergence (P<0.001) and chlorophyll content (P<0.05) of wheat. Increasing the IS9456 residue application rate from 7.2 to 14.4 g kg-1 soil increased the chlorophyll content of wheat. The timing of maize and wheat planting after sorghum residue incorporation may be critical.

Highlights

Maize (Zea mays L.), soybean [Glycine max (L.) Merr.] and wheat (Triticum aestivum L.) are important crops that are grown for food and industrial uses (Cox et al, 2019), and in some instances, sorghum is included in rotations that involve these crops
Maize dry weight was significantly higher when residues from IS22320 were incorporated than when residues from IS9456 were incorporated, in contrast to the emergence data
Averaged across the sorghum varieties, the maize plant dry weight, chlorophyll content and percent emergence significantly decreased (P

Summary

Introduction

In Zimbabwe, sorghum is primarily cultivated in drought-prone areas in agroecological Regions IV and V, which are classified as unsuitable for intensive cropping (Tibugari et al, 2020a). Maize (Zea mays L.), soybean [Glycine max (L.) Merr.] and wheat (Triticum aestivum L.) are important crops that are grown for food and industrial uses (Cox et al, 2019), and in some instances, sorghum is included in rotations that involve these crops. Sorghum, soybean, and winter wheat rotations are popular in some parts of the world (Hunter et al, 2019; Schlegel et al, 2019). Sorghum cover crops may be grown between cash crops such as soybean and wheat (NRCS-USDA, 2011). As such, when rotated with sorghum, these crops may be exposed to allelochemicals that are leached by sorghum residues (Silva, 2019)

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